The invention relates to a grip and guiding device for a directional drill for geotechnical drilling, especially rock drilling, more precisely a device as defined by the introductory part of claim 1, particularly for directional drilling with high precision in sedimentary species of rock.
A directional drill is described in NO C 168 962 which is provided with a locking device or packer which is supplied with drilling fluid under pressure in order to push out locking elements or pressure pads which can be brought in contact with the bore wall and lock the directional drill relative to the wall, so that rotation of the outer tubing of the directional drill is avoided. Such pressure pads may be utilised for locking an eccentric housing in a certain position or be used to bring upon the drill bit a skewed position, for thereby performing directional drilling.
From NO patent application Ser. No. 962744 is known a guidance tool for a rock drill where several pressure pads are arranged in at least two ring sections, so that the pressure pads become oriented in axial rows with projecting guiding bars oriented in a row. This solution is intended to reduce; the frictional forces, which are effective in the axial direction when the drill is moved forward and shall at the same time ensure a frictional force against rotation sufficient to avoid a rotational movement. The guidance is in this case ensured by a permanent eccentric housing positioned between the packer and the drill bit, known from the patent publication mentioned above.
A significant disadvantage with this known solution is that it requires several sets of pressure pads in rows in the length direction of the tool. The known rock drill requires the packer in the drill hole to be positioned centrically.
Directional drills are also known with several sensor controlled pressure pads arranged symmetrically around the periphery in order to provide a so-called xe2x80x9cmodulated pretensional forcexe2x80x9d. By activating the pressure pads independently is it possible to obtain a deviated position of the drill bit in relation to the main axis, and thus guide the drilling to obtain a directional drilling, i.e. drilling in a predetermined curved path. This solution, however, requires a complicated sensor system and a correspondingly complicated guidance mechanism, for the supply of pressure media to the several pressure pads. It is therefore costly and unreliable.
It is thus a main objective with the present invention to provide a directional drill with a grip and guidance system which is simpler than the known grip and guidance systems, and which provides a higher directional stability and higher versatility when used.
It is a particular objective to provide a directional drill which can be guided and repositioned with simpler means than the known directional drills. It is preferred to make use of a versatile directional drill, which can be used, in hard rocks as well as in sedimentary species of rocks. It is preferred to be able to drill both with a core tubing with an eccentric housing and alternatively with the deviation provider in the packer area, i.e. with an active eccenter.
It is a further objective to provide a directional drill with a grip and guidance system which can be used with a water hammer or another kind of drill hammer or drilling tool.
Further objectives of the invention will be disclosed by the more detailed description below.
The invention is defined by claim 1. Preferred embodiments of the invention are defined by the dependent claims 2-10.
The directional drill according to the invention is significantly simpler, and thereby more sturdy in use, than those previously known. This also gives the possibility to ensure a stable directional drilling by means of simple adjustment steps. Further details of the invention are disclosed by the example below.